DuckTales (2017) Season 3 Episode 2 The Depths of Cousin Fethry!

As Scrooge and the gang settle into their new underwater base, they receive an unexpected visit from Fethry Duck, who claims to have discovered a new species of creature lurking in the depths. Despite initial skepticism, Dewey and Webby agree to join Fethry on a deep-sea expedition to find the elusive creatures.

As they journey deeper into the ocean, the group encounters a variety of unusual and dangerous sea creatures, including a giant squid and a kraken-like monster. Along the way, they also learn more about Fethry's eccentric personality and love for scientific discoveries.

As they finally reach the location of the mysterious creatures, the group discovers a hidden underwater kingdom inhabited by mermaids and other mythical beings. However, their arrival is not met with a warm welcome, as the kingdom's ruler sees them as a threat to her secrets and orders her minions to attack.

Despite facing numerous obstacles and dangers, the group manages to overcome the mermaids' defenses and gain their trust. Along the way, they also uncover some shocking secrets about Fethry's past and motivations for discovering the new species.

In the end, the group successfully captures a specimen of the new creature and returns to their base, but not without some unexpected consequences and challenges. The episode ends on a cliffhanger, teasing future developments and adventures for the group.